Open loop print speed control

Abstract

A method enables adjustment of a print speed for a phase change ink imaging device with reference to an ink level sensor in a print head reservoir indicating an open loop or a closed loop state. The adjustment may also be made with reference to a measured image density, which may be a rolling solid area coverage average.

1. A method for controlling print speed of an imaging device, the method comprising:
 measuring an image density of at least a portion of a print job for the imaging device; 
 detecting a state of a level sensor for an ink level in a print head reservoir in the imaging device, the detected state indicating an open loop state or a closed loop state; 
 generating an estimate of a volume of ink in the print head reservoir with reference to the detected state of the level sensor; 
 comparing the estimate of the volume of ink to a threshold value; 
 adjusting a current print speed of the imaging device to a target speed in response to the estimate of the ink volume being less than the threshold value; 
 modifying the estimate of the volume of ink with an amount corresponding to a volume of melted ink added to the print head reservoir; and 
 transitioning the current print speed of the imaging device to a speed that is greater than the target speed with reference to a damping constant in response to the estimate of the ink volume indicating an ink level in the print head reservoir contacts a sensor in the printhead. 
 
     
     
       2. The method of  claim 1 , further comprising:
 selecting the target speed from a data structure with reference to the measured image density. 
 
     
     
       3. The method of  claim 1 , further comprising:
 setting the estimate of the volume of ink to a default volume that corresponds to a volume of ink in the reservoir that is below the level sensor in response to an open loop state being detected. 
 
     
     
       4. The method of  claim 3  wherein the damping constant corresponds to a rolling solid area coverage average. 
     
     
       5. The method of  claim 1 , the generation of the estimate of the volume of ink in the print head reservoir further comprising:
 subtracting an ink amount from the modified estimate of ink volume in response to ink being ejected from a print head. 
 
     
     
       6. The method of  claim 1 , the measurement of the image density further comprising:
 counting active pixels in image data of a page to be printed in the print job to obtain a rolling solid area coverage.